I've been, but only bought some andouille sausage. It's kind of barren looking, but definitely the place to go for Gulf seafood - they get crawfish from Louisiana once a week (friday?) and will cook it up for you. The guys there are pretty helpful.
My specialty is seafood and I can tell you that this place is not where you want to get it. The fish look like they've been sitting on the ice for days and the presentation (fillets sitting in a metal bin) doesn't help either. I wanted to try out their crawfish so I got a few pounds and took it home. To my horror, it was by far the nastiest stuff I've had and I've had bad crawfish before. They were overcooked and tasted like leather. I called the market to ask if I could either return or exchange my batch since they were inedible. The guy I spoke to basically said that it was not possible to help out in any way and that there was nothing wrong with the crawfish. I politely said ok and the conversation was over. I will never recommend the New Orleans Seafood Market (2212 Vernon st) to anyone.